Many modern day metals, such as those used in automobiles, are coated with one or more materials because the coatings are desired by the users of the metal to increase durability, reduce corrosion, etc. One example of a coated metal is galvanized steel. When a first piece of metal to be welded to a second piece of metal has a coating, the coating may be a factor that affects the weld process and may make the welding more difficult.
Additionally, if the coating weight and thickness varies along the surface of the metals, optimizing the weld process may be difficult and uniform welding may be hard to obtain.
Another element affecting welding of metals is that different oxides are formed at grain boundary surfaces and the oxidation points can affect functional part durability and fatigue strength of the weld.
Known methods of joining two pieces of sheet metal include resistance mash seam welding and laser lap welding.